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A208830
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G.f.: 1/(1-x) = Sum_{n>=0} a(n) * x^n / Product_{k=1..2*n-1} (1 + k*x).
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1
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1, 1, 2, 12, 132, 2196, 49836, 1447476, 51542868, 2182001316, 107319488412, 6024315658548, 380536243019220, 26739219616505076, 2070294450495377484, 175215334999701596724, 16099427228106472739988, 1596611582544914141925444, 170028864964367324939511036
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OFFSET
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0,3
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COMMENTS
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Compare g.f. to: 1/(1-x) = Sum_{n>=0} n!*x^n/Product_{k=1..n} (1 + k*x).
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LINKS
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EXAMPLE
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G.f.: 1/(1-x) = 1 + 1*x/(1+x) + 2*x^2/((1+x)*(1+2*x)*(1+3*x)) + 12*x^3/((1+x)*(1+2*x)*(1+3*x)*(1+4*x)*(1+5*x)) + 132*x^4/((1+x)*(1+2*x)*(1+3*x)*(1+4*x)*(1+5*x)*(1+6*x)*(1+7*x)) +...
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PROG
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(PARI) {a(n)=if(n==0, 1, 1-polcoeff(sum(k=0, n-1, a(k)*x^k/prod(j=1, 2*k-1, (1+j*x+x*O(x^n)) )), n))}
for(n=0, 20, print1(a(n), ", "))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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